Optical disks such as the compact disk (CD) or the digital versatile disk (DVD) have been diversified recently, and therefore availability thereof has been still growing from an information medium of reading-only to an optical information medium capable of writing. Synthetic resin, typically polycarbonate, having a low mold shrinkage ratio or a low expansion coefficient is used for substrate materials of the optical disk. Information is recorded on the surface of the substrate as a pit row in the case of the read-only disk, and a guide groove to become the track for laser is formed on the surface of the substrate in the case of the disk capable of writing. A multilayer film containing a writing layer is deposited on the surface to constitute the disk.
FIG. 11 shows an example of a structure of the writable optical disk in which a guide groove 101a guiding a laser beam from an optical head is formed on one surface of a transparent substrate 101 of polycarbonate of 0.6 mm in thickness, then a first dielectric material film layer 102, a phase change writing layer 103, a second dielectric material film layer 104 and a reflection layer 105 are deposited on the surface in this order, and further a UV-cured overcoat layer 106 is coated thereon. The optical disk of approximately 1.2 mm in thickness is obtained by laminating a substrate with films and another substrate 110 of polycarbonate of 0.6 mm in thickness through a lamination adhesive layer 107.
Because quantity of information to be recorded on a disk increases, a structure of the film that enables sure read has been required for densification of recorded information and acceleration of reading speed (Patent Document 1). In order to respond such requirement, it is necessary that the device forming the film should be much more improved on the performance thereof, for example, increasing the number of layers of the multilayer film, or regulating precisely the thickness of the layer.
For example, FIG. 12 shows the layer structure of DVD-RAM type in which a first dielectric material film layer 202, a first interfacial layer 203, a phase change recording layer 204, a second interfacial layer 205, a second dielectric material film layer 206, a thermal buffer layer 207, a reflection layer 208, an overcoat layer 209, an adhesive layer 210 and a substrate 211 of polycarbonate to become a cover are formed by laminating on the surface where a groove 201a of a substrate 201 is formed. Though layers from the first dielectric material layer 202 to the reflection layer 208 of the abovementioned layers are deposited together in one vacuum processing device, the number of film-depositing chambers in which each layer is deposited must be increased as the number of layers of the multilayer film is increased.
FIG. 13 shows an example of conventional vacuum processing devices for forming a multilayer film. A chamber 120 capable of maintaining in a vacuum state is provided with a load lock mechanism 121, and further first to eighth film-depositing chambers 122a to 122g are arranged in the chamber 120 together with a load lock mechanism 121 so as to be positioned along a circumference at the angular interval of 45 degrees on the circumference. A rotary carrying table 123 having an arm carrying a substrate is disposed at the center of the chamber 120, and rotates intermittently in a horizontal plane about a shaft 124 having an exhaust tube. A disk substrate carried from the load lock mechanism 121 is transported into the first film-depositing chamber 122a, and the film is deposited thereon by sputtering. Then, the substrate is transported into the second film-depositing chamber 122b and other film-depositing chambers in sequence so that a multilayer film can be deposited thereon, thereafter returns to the load lock mechanism 121 and is carried out from the chamber 120. The multilayer film-deposited substrate carried out is coated with the overcoat layer, and laminated with the substrate of polycarbonate of 0.6 mm in thickness through a lamination adhesive layer in order that an optical disk can be obtained. In the above, multilayer film-depositing tact is rate-determined by the film-depositing chamber that requires the most time for film-depositing.
In a general vacuum processing device, a substrate of the object to be processed is carried on the rotary carrying table disposed in the chamber, and is transported to the film-depositing chambers disposed on a circumference with an interval for overlapped film-depositing. Because the number of the film-depositing chambers is increased as the number of layers in the multilayer film increases, the radius of the circumference becomes large. As a result, the dimension of the chamber containing the rotary carrying table is enlarged. Therefore, because the volume to be evacuated increases remarkably, the volume of the exhaust system evacuating to a vacuum state must be increased to the extent beyond necessity, and enlarged. Additionally, carrying circumference for the processed object on the rotary carrying table becomes large, so that the centrifugal force subject to the processed object cannot be neglected when the rotary carrying table is rotated with a high speed to shorten the tact time. Furthermore, intermittent drive control of the rotary carrying table becomes complicated.
Patent Document 1: Japanese Patent Laid-open No. 2001-209974